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  #16 (permalink)  
Old 05-01-2011, 08:31 PM
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Quote:
Originally Posted by AllRi5e
Carb has vac secondaries. Suppose to be plug a play for cars under 450hp. I think someone messed with it and returned it.

Would tight valves cause this? I did install the rockers myself and it was my first shot at it.

Vacuum 17-19", the gauge shakes back and forth.

I spray the carb base plate and intake with carb spray and listened for any change in idle. No change.
Yes, tight valves could cause it. Shaking gauge indicates a valve that isn't closing (or cracked rings, or a few other issues that aren't likely with a new engine assembly)

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  #17 (permalink)  
Old 05-01-2011, 08:31 PM
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Quote:
Originally Posted by AllRi5e
At 60* it idles roughly at 1300

I used my digital light with this MSD before and it worked fine. I thought the gun could be wrong after I relocated the battery so I bought the cheap one and got the same reading.

Is it possible to compensate bad mix with advanced timing?

20* is a no go. Once I get below 40 the rpm starts dropping, it starts shuddering and dies.

I was thinking weak spark but I didn't think the MSD could "do" weak spark.
MSD can do weak spark and since your #1 cylinder has a good spark you'll read everything fine with your light. You could have 1 or more dead cylinders or maybe a wire crossed? You might be able to use the timing light to test for a spark by just timing off each of the other cylinders (just looks for the light to flash but disregard the timing readings). The MSD is probably working fine but the sparks not getting to where it should. Just a guess, could be as others suggest.

60' is insanely high and if thats accurate its going to cause damage eventually. At least get down to below 40 if you can and work on it at idle from there.

How well adjusted is the carb idle mixtures and idle speed screw? If you drop below 30' timing can you increase the idle speed (with the screw on the card) to keep it running or does it still die?
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Old 05-01-2011, 08:46 PM
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Quote:
Originally Posted by curtis73
First I would do is verify TDC. Its pretty common for balancer rings to slip on the rubber ring, so the timing mark isn't always a good indicator. Don't worry about being a tooth off... that is only a problem with points ignition. With more modern ignitions, it doesn't matter what tooth its on you just turn the dizzy until its lined up right.

Second I would verify the carb tune. Look down the throats while its idling. Is there liquid fuel dripping from the boosters? If there is, chances are its a blown power valve or a needle/float issue.

This is assuming that you have the firing order right. I know, its a stupid thing for me to say, but I have chased all kinds of issues only to find out that I skipped the basics.

Help us out.... cam specs and compression?
I turned the idle screws all the way in and the engine died. So, the valve is power valve is working. At least, that was how Holley siad to test it.

Don't sweat the firing order thing, it would be cool if that was it. I once couldn't get a car started, only to realize I didn't ground the engine.

I checked the firing order and wire placement several times.

Compression test reults were 160-170 across the board.

Cam is Comp Thumpr
lift .479 intake .465 exh
duration .319/ .310
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  #19 (permalink)  
Old 05-01-2011, 08:54 PM
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Quote:
Originally Posted by bubbahotep
MSD can do weak spark and since your #1 cylinder has a good spark you'll read everything fine with your light. You could have 1 or more dead cylinders or maybe a wire crossed? You might be able to use the timing light to test for a spark by just timing off each of the other cylinders (just looks for the light to flash but disregard the timing readings). The MSD is probably working fine but the sparks not getting to where it should. Just a guess, could be as others suggest.

60' is insanely high and if thats accurate its going to cause damage eventually. At least get down to below 40 if you can and work on it at idle from there.

How well adjusted is the carb idle mixtures and idle speed screw? If you drop below 30' timing can you increase the idle speed (with the screw on the card) to keep it running or does it still die?
It'll fire at 30* but won't start, I tried increasing the curb idle to compensate but it just dies.

Its a new engine with a ton of new parts, I hate to damage it. Dialing it back to 30 and trying to start it from there seems safer than waiting for it to detonate itself to death. My starter doesn't like cranking it at 60 anyway.

Could a faulty pick up module or coil cause weak spark? I read that these parts either work or don't.
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Old 05-01-2011, 09:10 PM
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Quote:
Originally Posted by curtis73
Yes, tight valves could cause it. Shaking gauge indicates a valve that isn't closing (or cracked rings, or a few other issues that aren't likely with a new engine assembly)

If I had a valve or two that were not closing, my compression test would show it? Would a "leak down" tell me more?
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Old 05-01-2011, 09:17 PM
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did you have the 1.6 rockers on the other heads? if not ,pushrod length- was the cam degreed ? almost sounds like a flat lobe but you said had good compression on all 8 .just throwing out an idea or two
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Old 05-01-2011, 09:17 PM
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Comp Thumpr. How many times are we going to read posts from guys that could not get their engine tuned with one of these turds installed in their engine? Too much overlap means not enough vacuum signal at idle for the carb to function.

OP, do you mean to tell us that your initial timing is set at 40 degrees tdc with an HEI that adds 20 degrees more mechanical advance? How would you even get the engine to turn over? Check your timing light or your balancer. One of them it totally out of whack.
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  #23 (permalink)  
Old 05-01-2011, 09:45 PM
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Quote:
Originally Posted by 1932bantam
did you have the 1.6 rockers on the other heads? if not ,pushrod length- was the cam degreed ? almost sounds like a flat lobe but you said had good compression on all 8 .just throwing out an idea or two
No, I had stock rockers on the old heads. The head builder sold me longer pushrods for this setup. I did not degree the the cam. I don't know if its "good" compression, but its even across all cylinders.
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  #24 (permalink)  
Old 05-01-2011, 09:53 PM
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Quote:
Originally Posted by cool rockin daddy
Comp Thumpr. How many times are we going to read posts from guys that could not get their engine tuned with one of these turds installed in their engine? Too much overlap means not enough vacuum signal at idle for the carb to function.

OP, do you mean to tell us that your initial timing is set at 40 degrees tdc with an HEI that adds 20 degrees more mechanical advance? How would you even get the engine to turn over? Check your timing light or your balancer. One of them it totally out of whack.
Initial timing is 60 degrees. I know its crazy. I've used two timing lights and I'm checked TDC from the mark on the balancer to the rockers no less than 10 times. I have a high torque Hitachi starter. I don't think a stock starter would crank the engine like this.

I now know the cam isn't great. I would have gone full roller if I knew how the cam was before I bought the engine. If I have to remove the intake I will swap it out.
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  #25 (permalink)  
Old 05-01-2011, 10:03 PM
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I'm just trying to gather as many ideas as possible before I take my last stab at this thing.

Valves being too tight could cause this. Whats the best way to attack that? Back all the rockers off a turn?

How about a spark issue? Bad coil or pick up? Is it possible? My MSD isn't grounded at the battery like MSD likes, its grounded at the block.

I've seen similar post to mine but no one posts the solution. I'll try everyone's ideas and report back. If I have to take it to shop, I'll report those results as well.
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  #26 (permalink)  
Old 05-01-2011, 10:04 PM
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It is surprising that a cam with that duration would pull 17-19"wg vacuum, must be an inaccurate gage.

The compression test may rule out valves being held open from poor valve adjustment.

Yeah the thumper cam blues is becoming a familar tune but the engine ran OK before the head swap?

I am thinking intake gasket seal failure or misallignment (not the carb gasket)

Also you should use a piston stop and verify TDC not the rocker arm position. I doubt it is actually 60 inital, check for true TDC:

http://www.crankshaftcoalition.com/w...op_dead_center
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  #27 (permalink)  
Old 05-02-2011, 04:40 PM
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I was running a vertex mag i bought used in a blown motor .Not knowing much then, I figured it was locked out so i set timing in at 38* with a buzz box .ran good ,Used roller cam also lined up timing marks didn't degree, ran a 9.89 on alky, come to find out after had to have new coil in mag it had 15* in mag total of 53 * (damn) we took blower off and installed just a carb this thing would not idle at all taking in accont the 15* had to keep advancing it to run. after a lot of calls we degreed the cam,It was off a bunch. woola ran like a champ. (blower will cover a lot of bad tuning). Also your stock rockers are 1.5 you changed to 1.6's did he just sell you a set of longer p rods or did he check it to see what was actually needed?
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  #28 (permalink)  
Old 05-02-2011, 05:23 PM
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If it wont idle under 40* and you can make it idle at 60 something is wrong with your procedure or your balancer. You have good compression so most likely your cam timing is ok.

Moving the wires on the cap will accomplish nothing as you will then need to move the distributor body to get it to run again and will be back in the same situation.

If the vacuum is jumping you most likely have a tight valve. I like to adjust them with the engine running but it can get messy if you dont have a set of valve covers you can cut up.

60* is way off, more than 1 cylinder in the firing order. Each cylinder represents 45* of the order.

Start with the simple stuff first, make sure you are on #1 wire, check firing order again, pay special attention to 5 and 7 as they are easy to mees up. Check for tight valves, this could affect the way it runs but will not affect the timing issue.

Have you tried turning the idle up and backing the timing down in steps. Is it possible the idle is just set to low.
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  #29 (permalink)  
Old 05-02-2011, 08:38 PM
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Start over. Pull the heads. Change the gaskets. Verify piston at TDC before putting heads back on. Verify where the timing mark on balancer is. CHANGE THE CAM AND THROW THE THUMPR INTO A LAKE AS FAR AS YOU CAN THROW IT. Put heads back on engine. Follow any one of the trued and tried methods of setting the valves. Something is way wrong with your setup and starting over is the only way to get to the bottom of it.
Good luck.
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  #30 (permalink)  
Old 05-02-2011, 08:40 PM
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you need to use a dead stop on # 1cylinder to verify the harmonic balancer is ligning up with the timing pointer, if it is'nt ligning up either you are using the wrong timing cover or balancer , or the balancer has spun on its rubber ring, an other problem could be a bad distributor ( i seen a few chevy 4.3 and 5.7 engine be working bad and put the timing light on them and the timing would at 40 plus degrees with no one adjusting the timing, the star wheel is usually cracked or has spun on the distributor.
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